Why is the Nixon v US case a landmark case?

Nixon v. United States (1974) is a landmark case because it affirmed the principle that no person, including the President, is above the law. The Supreme Court unanimously ruled that President Nixon could not claim "executive privilege" to withhold information relevant to a criminal investigation, specifically regarding the Watergate scandal. This decision reinforced the accountability of government officials and established a precedent for the limits of presidential power, significantly impacting the balance of power among the branches of government.